How to convert cm to px in a screen?

Never report px in a research paper when you want to communicate about a stimulus size on screen, it is not a sign of reproducibility because the pixel size of my screen is not necessarily the same pixel size than yours.

All three of these have 1920x1080 px screens. – gronostaj in this forum

The variables / constants you must have are :

• distanceFromScreen usually 50 cm (Yung et al., 2015)
• pxPerDeg (to compute it, you can use this calculator)
• expectedStimulusSizeWidth

Here is the JS code to compute the expected size (in cm) of a stimuli :

const   stimWidthRad = 2 * Math.atan((expectedStimulusSizeWidth / 2) / distanceFromScreen); // stimulus width in radian
const   stimWidthDeg = stimWidthRad * 180 / Math.PI; // stimulus width in degrees
const   stimWidthPx = stimWidthDeg * pxPerDeg; // stim width in px from real monitor size in cm.